Peptide / SubQ, Intranasal / 0.25-0.5mg every 2-3 days
Melanotan II*
Melanotan II was designed at the University of Arizona in 1989 as a tanning drug: the pigment hormone alpha-MSH cut down to seven residues and stapled into a ring so it would survive long enough in blood to work. It reached three human volunteers in a 1996 pilot study, was tested in two small placebo-controlled erectile-dysfunction studies, and was never developed into a licensed product, so the grey market has been the route to human use ever since.
In plain words
Melanotan II is a lab-made, ring-shaped copy of alpha-MSH, the hormone that tells skin cells to make pigment. People inject it to tan without sun, and because the same message reaches other receptors it also triggers erections, an effect that arrives together with the tanning and cannot be dialed apart by dose alone; reduced appetite has been seen in animal work and was noted only as a passing side effect in the human studies, which did not measure it. The human evidence is very small: the only published tanning study gave it to three men, two of whom got darker, and the two studies of its erection effect enrolled ten men each. It has never been approved anywhere and is sold as an unlicensed product; two relatives of it did reach approval, but those are different molecules with narrow, specific uses. The reported harms are not minor: severe nausea limited the dose in the published studies, case reports describe existing moles darkening and new ones appearing within a day of a single injection, one report describes a melanoma found in a user, which a single case cannot prove the peptide caused, and one 6 mg injection put a man in intensive care for three days with a racing heart and muscle breakdown. There is also a supply problem: when a laboratory measured vials bought online, all were labeled 10 mg and none held 10 mg, so what is in the vial can be far less than the label says.
At a glance
| Half-life | 0.042 days |
|---|---|
| Tmax | 0.02 days |
| Route(s) | SubQ, Intranasal |
| Published dosing range | 0.25-0.5mg every 2-3 days |
| Vial strengths | 10, 5 mg |
Reference data from the DosePlot canon -- not a protocol recommendation.
Serum curve
Single 0.375 mg dose by SubQ, rendered from the same engine that powers the interactive chart. Relative levels, not lab values.
What does the evidence show?
Two things are labeled separately here because they answer different questions. The tier is how a study was built. The distance chips are whether that study touched this molecule, by this route, in a population resembling the reader. A randomized trial of a different molecule keeps its tier and still says nothing about this compound.
| Finding | Tier | Distance from use | Study |
|---|---|---|---|
| The only published human study of melanotan II as a tanning agent enrolled three men. Over two weeks of subcutaneous injections escalating from 0.01 to 0.03 mg/kg, two of the three showed increased pigmentation of the face, upper body and buttocks, measured both by instrument and by eye one week after the last dose. The report concluded that tanning followed as few as five low doses given every other day, and recommended 0.025 mg/kg per day for further study. No larger trial of that indication was ever published. | clinical | not recorded | Dorr RT, Lines R, Levine N, et al. Evaluation of melanotan-II, a superpotent cyclic melanotropic peptide in a pilot phase-I clinical study.Life Sciences 58(20):1777-1784, 1996 |
| In ten men with erectile dysfunction of no known physical cause, injection produced clinically apparent erections in eight. Measured over six hours with a rigidity monitor, mean time above 80 percent tip rigidity was 38.0 minutes on melanotan II against 3.0 minutes on placebo (p = 0.0045). The design was double-blind, placebo-controlled and crossover, but ten men is a small sample and the finding has never been repeated at scale. | clinical | not recorded | Wessells H, Fuciarelli K, Hansen J, et al. Synthetic melanotropic peptide initiates erections in men with psychogenic erectile dysfunction: double-blind, placebo controlled crossover study.Journal of Urology 160(2):389-393, 1998 |
| A second crossover study, in ten men whose erectile dysfunction had a physical cause, used 0.025 mg/kg. Subjectively reported erections followed 12 of 19 active injections against 1 of 21 placebo injections; mean time above 80 percent tip rigidity was 45.3 minutes against 1.9; self-rated sexual desire was higher after the drug. Severe nausea accompanied 4 of the 19 active injections, which is the practical ceiling on the dose. | clinical | not recorded | Wessells H, Gralnek D, Dorr R, et al. Effect of an alpha-melanocyte stimulating hormone analog on penile erection and sexual desire in men with organic erectile dysfunction.Urology 56(4):641-646, 2000 |
| Appetite suppression is a receptor effect rather than an incidental one. Injected directly into the brain ventricles of mice, melanotan II suppressed feeding in four separate models of overeating, including fasted animals and genetically obese ob/ob mice. A melanocortin antagonist abolished the effect and, given alone, increased feeding. The human record is one study, not several: decreased appetite is listed among the transient side effects of the 1998 crossover study in men with psychogenic erectile dysfunction (Wessells and colleagues, Journal of Urology, 1998), while the 2000 study in men with organic causes reports nausea and stretching or yawning without it. Appetite was an endpoint in neither. | preclinical | not recorded | Fan W, Boston BA, Kesterson RA, Hruby VJ, Cone RD. Role of melanocortinergic neurons in feeding and the agouti obesity syndrome.Nature 385(6612):165-168, 1997 |
| Pigmented lesions can change quickly. A case report describes new melanocytic nevi erupting and pre-existing nevi darkening within 24 hours of a single injection of melanotan II. Independent eruptive-nevus reports have appeared in the dermatology literature since 2009. These are case reports: they establish that the change happens, not how often, and not what it means for melanoma risk. | clinical | not recorded | Schulze F, Erdmann H, Hardkop LH, et al. Eruptive naevi and darkening of pre-existing naevi 24 h after a single mono-dose injection of melanotan II.European Journal of Dermatology 24(1):107-109, 2014 |
| A single 6 mg subcutaneous dose, six times what the user understood to be a starting dose, sent a 39-year-old man to intensive care with agitation, sweating, dilated pupils, tremor, a heart rate peaking at 146 beats per minute and rhabdomyolysis. Creatine kinase rose to 17,773 IU/L and creatinine to 2.25 mg/dL; he was discharged from intensive care after three days. Mass spectrometry confirmed the injected material was melanotan II. | clinical | not recorded | Nelson ME, Bryant SM, Aks SE. Melanotan II injection resulting in systemic toxicity and rhabdomyolysis.Clinical Toxicology 50(10):1169-1173, 2012 |
| Community practice starts far below the published phase I dose and spreads it out: roughly 0.25 to 0.5 mg every second or third day, often taken in the evening, with the first few doses smaller still. The stated reasons are nausea and facial flushing, both of which are reported to fade over the first week or two while pigmentation accumulates, and both of which return if dosing restarts after a gap. | anecdotal | not recorded | community reports aggregated from reddit, MESO-Rx, and similar forumsno study |
How did it get here?
- preclinical1980
- A University of Arizona group makes two substitutions in alpha-MSH, the body's own pigment hormone: the methionine at position 4 becomes norleucine, and the phenylalanine at position 7 is replaced by its mirror image. The result, [Nle4, D-Phe7]-alpha-MSH, is 26 times as potent as alpha-MSH in the adenylate cyclase assay and resists breakdown by serum enzymes. It is later called melanotan-I.
- preclinical1989
- The same group shortens the hormone to residues 4 through 10 and ties the fragment closed, joining an aspartic acid side chain at position 5 to a lysine side chain at position 10 through an amide bond. The cyclic product, melanotan II, is about 100 times as potent as alpha-MSH in the lizard skin bioassay, and the 23-membered ring keeps acting after smaller rings have stopped. A companion paper the same year narrows the active core to four residues, His-Phe-Arg-Trp, which the cyclization leaves in place.
- first-human1996
- Dorr and colleagues publish the pilot phase I study: three male volunteers, subcutaneous injection, doses from 0.01 to 0.03 mg/kg. Two tan. Alongside that, the subjects report nausea, stretching and yawning, and spontaneous erections lasting one to five hours after each injection. All of it is recorded in the adverse-effect column.
- first-human1998-2000
- Two small crossover studies test the adverse effect as the indication, first in men with psychogenic erectile dysfunction and then in men with a physical cause. Both are positive, and both are limited by nausea. Development shifts to bremelanotide, a structural variant aimed squarely at sexual function. Neither crossover publication assigns a phase, and both are placebo-controlled efficacy studies in patients, which is phase II work by design. What melanotan II never gets is a registration program: no phase III trial, and no marketing authorization anywhere.
- grey-market2009-2015
- Melanotan I and II turn up for sale over the internet as tanning injections, unlicensed, with use reported to be common among young people attending fitness centers; the BMJ documents use in the general population in 2009. A laboratory group buys melanotan II from three online shops and measures what is in the vials, publishing the results online in April 2014 and in a February 2015 print issue. Every vial is sold as 10 mg. The measured content is 4.32 to 8.84 mg, with unidentified impurities at 4.1 to 5.9 percent in two of the three products.
- grey-market2019-2026
- The molecules that reach approval are melanotan II's relatives, not melanotan II. Bremelanotide is approved in the United States in June 2019 at 1.75 mg per autoinjector, on the strength of two randomized phase 3 trials, and its label is narrow: premenopausal women with acquired, generalized hypoactive sexual desire disorder, not postmenopausal women and not men. Afamelanotide, which is the linear melanotan-I, is approved in October of the same year as a 16 mg implant, to increase pain free light exposure in adults with a history of phototoxic reactions from erythropoietic protoporphyria. Melanotan II holds no marketing authorization anywhere, and it keeps selling unlicensed in more than one form: a 2025 case report describes a 22-year-old woman who used a melanotan II nasal spray to tan and was found to have an oral mucosal malignant melanoma, which the authors report as a possible association rather than a demonstrated cause.
How is it made?
Production happens in four stages.
1. Building the chain. Melanotan II is assembled by solid-phase peptide synthesis, the standard method for short peptides. The chain grows one amino acid at a time on a resin bead, starting at the C-terminal end, with every reactive side group masked so only the intended bond forms. Two of the seven residues are not ordinary building blocks: norleucine at position 4, and phenylalanine in its mirror-image D form at position 7.
2. Closing the ring. The side-chain masks on the aspartic acid at position 5 and the lysine at position 10 come off on their own, and the two are joined by an amide bond. That turns a straight chain into a ring. The original route closed the bridge either on the resin, where chains sit far enough apart to react with themselves, or in solution, where high dilution does the same job.
3. Cleaving and purifying. Acid releases the peptide from the resin and strips the remaining protecting groups. Each coupling is slightly incomplete, so the crude material carries deletion sequences alongside the target. Reverse-phase chromatography separates them, and mass spectrometry confirms what comes off the column.
4. Filling. The purified peptide is dissolved, sterile-filtered, dispensed into vials and freeze-dried, which is why it arrives as a dry cake to be reconstituted.
The synthesis itself is routine. What varies outside regulated manufacturing is how far the purification was pushed, how much peptide the vial actually holds, and whether the fill was sterile.
Worth knowing
The number on the label is not the number in the vial. When a laboratory group bought melanotan II from three online shops and measured it, every vial was sold as 10 mg and none held 10 mg: the measured range was 4.32 to 8.84 mg, and the products from two of the three shops carried unidentified impurities at 4.1 to 5.9 percent. Reconstitution arithmetic is done against the label figure, so a vial holding 4.32 mg delivers about 43 percent of every dose calculated from it. The error never changes a number on the syringe, which is why nothing about it looks wrong.
Breindahl T, Evans-Brown M, Hindersson P, et al. Identification and characterization by LC-UV-MS/MS of melanotan II skin-tanning products sold illegally on the Internet.Drug Testing and Analysis 7(2):164-172, 2015
The side effect became the drug. In the 1996 pilot study the erections sat in the adverse-effect column next to the nausea and the yawning, described as lasting one to five hours after each injection in men who had been given the peptide to see whether it would tan them. Within two years the same investigators were running erectile-dysfunction trials with that response as the endpoint, and the descendant molecule that eventually reached a pharmacy shelf, bremelanotide, exists because of it.
Dorr RT, Lines R, Levine N, et al. Evaluation of melanotan-II, a superpotent cyclic melanotropic peptide in a pilot phase-I clinical study.Life Sciences 58(20):1777-1784, 1996
A 2014 case report describes a 20-year-old woman with fair skin who self-injected melanotan II for three to four weeks to deepen a sunbed tan, and had a cutaneous melanoma excised from her left buttock three months later. The authors are careful about what they are reporting. The melanoma coincided in time with both the peptide and the sunbed use, and one case cannot separate the two or show that either caused it.
Hjuler KF, Lorentzen HF. Melanoma associated with the use of melanotan-II.Dermatology 228(1):34-36, 2014
Reconstitution
Melanotan II* ships lyophilized and is mixed before use; the published vial strengths are 10, 5 mg. The water volume you add sets the concentration, not the dose -- the calculator turns a vial size and a water volume into mg/mL, draw volume, and units on an insulin syringe.
Open in the reconstitution calculatorWritten and reviewed by Evan Marlow, developer of DosePlot · Updated 2026-08-27
Not medical advice. DosePlot is an informational tool, not a healthcare provider, and using it creates no provider-patient relationship. Do not start, stop, or change any protocol without the approval of a licensed healthcare professional.
Your whole protocol, in one place.
Free to start. Runs in your browser today.
14-day Premium trial inside, no card required.
Launch the web app